Leather dyed with mono-or disazo dyestuffs



Patented Mar. 8, 1938 UNITED STATES P TENT OFFICE LEATHER DYED 'WITH MONO- R DISAZO DYESTUFFS N0 Drawing. Application March 18,1936, Serial No. 69,592. In Germany March 23,,1935

4 Claims.

The present invention relates to leather dyed with certain monoor disazodyestuffs, more particularly it relates to leather which has been dyed with monoor disazodyestufis of the general formula:

In the said formula R stands for the radical of an aromatic diazo compound or a diazoazo com-' pound derived from a monamine or monamines respectively, B. stands for a 2-aminonaphtholcoupling component or a substitution product thereof, especially of such a substitution product ingwhich a hydrogen atom of the amino group is substituted by alkyl or aryl or substituted alkyl or aryl, e. g. the sulfo or carboxylic acids thereof, and n stands for a whole number, such as for 1, 2, 3 or 4 etc.

In dyeing chrome leather, it is desired not only to dye the surface of the leather, but also to give an even shade to the cut of the leather to a certain depth of penetration, while the zone of the cross-cut remaining undyed is intended to retain the pure greenish chrome color.

Of particular technical importance are dyeings of this kind on leathers, the grain side or flesh side of which is more or less ground off after the dyeing.

In accordance with the present invention the desired effect is attained to an excellent degree, when in the dyeing process monoor disazodyestuffs of the above identified formula are used, the dyeing per se being performed according to the standard methods of dyeing leather, as is more fully described in the annexed examples. If desired the monoor disazodyestufis of the above identified formula can be used in mixture with other acid or substantive dyestuffs.

The invention is illustrated by the following examples, without being restricted thereto:

Example 1.100 kgs. of neutralized chrome calf leather are introduced into a drum with about 300 kgs. of water at 60 C. A dyestuif solution is gradually added prepared from 1 kg. of the dyestuif from diazotized p-sulfanilic acid coupled with phenyl gamma acid (alkaline coupling) and 25 kgs. of hot water. After half an hour, the dyestuif has been absorbed almost without residue. Stuffing of the leather is then effected. In. this manner, there is obtained a dyeing of a useful brown' shade, which exhibits on the grain side and on the flesh side a distinct dyeing'of the cut, without change of the characteristic greenish color of the chrome leather in the interior of the cut. After glac finishing such leathers exhibit an improvement of covering and equalizing properties in comparison with leathers dyed with dyestufls which do not dye in the'grain in the manner "described. Further, the flesh side can be easily ground off, an operation which is usual inpmany' cases, without producing a bad and ununiform appearance by the standing out of undyed fibers.

Example 2.-100 kgs. of dry and ground off chrome calf velours leather are dyed, after a good egging in 500 kgs. of hot water, with 5 kgs. of the dyestufi obtained from diazotized sulfanilic acid coupled in an alkaline medium with 1 molecular proportion of a mixture of 60% phenyl-gamma-acid and 40% phenyl-J-acid. In order entirely to exhaust the dye bath, it is acidifled with formic acid, and finally, as usual for velours leather, the latter is subjected to some degree of stufiing.

There are obtained dyeings of a reddish brown shade, which exhibit a very strong dyeing in the grain. The leathers dyed in this manner show a good fastness to grinding 01f and to water, and there is not the lightening of shade, which in other cases is a troublesome result of regrinding.

Example 3.-l00 kgs. of chrome tanned and neutralized horse leather are dyed in a bath with 0.75 kgs. of the dyestuff from diazotized l-nitraniline-2-sulfonic acid coupled with phenylgamma acid (acid coupling) with the addition to the bath of 0.75 kgs. of direct deep black E extra (Schultz Farbstofftabellen 1931, p. 271),

and then stuffed. The leather dyed in this man- The following table contains some further exin which R. stands for a member selected from' amples and the shades obtained on leather:

7 the group consisting of radicals of diam and diazoazo compounds derived from monamines, R

I monaminenof thevbenzena'series and R. for the Diazo components 7 Coupling oombonents Shade 5 7 consisting of radicals of 2-aminonaphthol-c0uv O-Sulphanilio acid Phenyl gamma acid (alka- Brown D g components and 0f N-substitution P u 1 line coupling) thereof, and n stands for a whole n mber.

mfi f (alkalm 3 2. Leather dyed with a dyestufi of the general z-na hthylamine-4.8-di- Phpnyl gamma acid (alka- Brown formula: 1o sul onic acid 7 lme coupling) Q V r Aniline m-Garboqnhenylgammw =Beddish ;1

m V 7 t acld(alkaime coupling) brown r (smrr) Amino-ambeniene; 2 S-aminonaphth -3 6-di- V i o l a t a I a sulioiid: )acid (alkaline rown i h t d f 1 h d1 f d1 7 d 0 a i whtl azo 4- niiaraniline 2 -sulionic Phenglgamma acid (acid n c R s an s or t e Ia cal o a tize ac E'nitro-Z-anisidine 4-sulionic acid 2 'nitraniline-d sulfonic Aminoazobenzene disul oouplm n Phenyl gamma -acid-(acid oouping) Phenyi-I'acid (acid cou 8 naphthol -6 sulionfd g 'radicaluot a} 2-aminonaphthol-ooupling compo- 3328; 'nn't inwhich one hydrogen atom of the amino Y n v ish grQiip- 'is supstituted by-aryLand 1:. stands for a gffifgi whol'eimmber. a .Jjrotnx i 3. Leatheredyd 'mithJhedyestuff having in thefitreeistateiths following formula:

ionicacid plimz) 1 Do--. YhenyigammaacidKalka l line coupling)- v if, N=N NEG Besides:thefiexdilentsdyeini; iobtainedseiin at r;' H0 rm neutral bath; 1 the dye'stuflsz-rhavei a good; stability to al'kalies'iiand aeidszand'in gener Iastness to alkalies andsacidsmzi they can also be usedetogetlren'withbthenisnitable W- wezclaim: h

1. Leather dyed-*avithiatdye stumof the-generala formula-:1

acid or substantive J dyestuflsn s s 4; Lathr-dyedavitn free'state the'following formula:

stands for a member selected from the group '7 dyestuflhaving'irrthe 

